Process for pulping wood chips with sodium sulfide and organic solvent



May 19, 1970 D. STARR ETAL PROCESS FOR PULPING WOOD CHIPS WITH SODIUMSULFIDE AND ORGANIC SOLVENT Filed Jan. 13, 1967 ATTORNEYS United StatesPatent O 3,513,068 PROCESS FOR PULPING WOOD CHIPS WITH SODIUM SULFIDEAND ORGANIC SOLVENT Laurence D. Starr and Ronald L. Casebier, Shelton,Wash., assiguors to Rayonier Incorporated, New York,

N.Y., a corporation of Delaware Filed .Ian. 13, 1967, Ser. No. 609,103Int. Cl. D21c 3/20 U.S. Cl. 162-76 6 Claims ABSTRACT OF THE DISCLOSUREIn the process of this invention wood chips are digested in a solutionconsisting essentially of an organic solvent for degraded lignin,preferably a sulfone, and 9 to 15 of active alkali added as sodiumsulfide, providing essentially the entire active alkali in aqueoussolution resulting in a pulp having eyceptionally high I.V. values inthe range of abo-ut 12 to 18, and in yields as high as 60%.

The separation of lignin from wood by extraction with organic solventsin which lignin is soluble has been the subject of considerable researchfor many years but we are not aware of any organic solvent extractionprocess which has reached the level of commercial acceptance.

This invention is based on our discovery that wood chips digested in anaqueous alkaline solution of sodium sulfide and an organic solvent fordegraded lignin give pulp having unexpected high I.V. values and highpulp yields, and other important results. In accordance with ourinvention we employ the combination of a relatively mild 100% suliditypulping solution which means that the solution is substantially free ofadded sodium hydroxide the active alkali being provided with sodium sul*fide and an organic solvent for degraded lignin such as a sulfone.

Suitable organic lignin solvents for use in this invention include alkylpolyols such as ethylene glycol and the cyclic or acyclic sulfones.Successful digestions have been run in the laboratory using ethyleneglycol, sulfolane, dimethyl sulfone, di-n-propyl sulfone, di-n-butylsulfone and 3-methyl sulfolane with the sulfolane so far giving the bestover-all results.

The organic solvent appears to dissolve and remove degraded lignin Whilethe mild sodium sulfide solution does not appreciably degrade thecarbohydrate portions of the Wood such as results with strong causticsolutions. In addition, the presence of the lign solvent appears to helpprevent reprecipitation of dissolved lignin onto the carbohydrate orcombination therewith during the cooking process. In any event, a usefulform of lignin appears to be obtainable as a by-product from the spentliquor. Recovery of the solvent solution from the spent liquor alsoappears feasible in commercial operations. A typical combinationsolution comprises an approximately one to one aqueous solution of theorganic solvent containing from 9 to 15% of active alkali added assodium sulfide and expressed as NagO. A practical digestion solution toWood chip ratio is :1 and the digestion can be eiciently carried out atabout 170 C. in less than three hours. The digestion of pulp in suchsolution results in a sharply increased cuene I.V., as high as 18 andincreased yields as high as 60%, without any in- 3,513,068 Patented May19, 1970 lCe creased cooking time or temperature. The product chipsleaving the cooking vessel will usually require mechanicaldisintegration by some means such as afforded by a Sprout-Waldronrefiner and will have a relatively high K number, yet the chlorited pulpwill completely dissolve in cuene.

Pulps produced lby this method have several unique properties. Thesepulps are completely soluble in cuene after chloriting. Cuene viscosity,therefore, permits a good estimation of the true intrinsic viscosity.Intrinsic viscosities of these pulps in cuene are usually high andcorrespond roughly to a nitrate degree of polymerization (D.P.) of 2,500to 2,900. These are exceptionally high for wood derived carbohydratesand are similar to chemical cottons which have relatively high molecularweights. This D.P. range is also not far removed from that of nativecellulose, starting at 3,500.

Total hemicullulose content for these pulps has varied from 12.2 to15.7%. Several possibilities arise from the apparent high D.P. of thepulps:

(1) The high cuene LV. may indicate that the hemicelluloses present arealso of an exceptionally high degree of polymerization.

(2) If the hemicelluloses present are similar in molecular weight tothose found in conventional pulps, then the cellulose must be ofexceptionally high degree of polymerization-greater than 2,900.

(3) Non-cellulosic artifacts present in the pulps may account for thehigh viscosity of the cuene-pulp solution.

The cooking procedure used in the following examples was as follows:wood chips, organic solvent, water and sodium sulfide (NaZS) were placedin an 1150-ml. capacity stainless steel reactor in the proportionsindicated. Suicient wood chips to provide grams of wood on an oven-drybasis, a total of 750 grams of organic solvent and water proportionedbetween the two as indicated, and sufiicient NazS to give the indicatedactive alkali content (A.A.) to the mixture were placed in the reactor.The reactor was then sealed, attached to a slowly rotating spindle andthe contents heated to the desired temperature in, and for, the derivedperiods of time. The cooked Wood chips were then cooled, removed fromthe reactor, drained on a screen, mechanically beaten briefly in twoliters of 1% aqueous NaOH solution (to prevent reprecipitation ofsolubilized lignin and to break up the chips into fibers), centrifuged,washed an dried. The tests made on the pulp as indicated in the variousexamples and tables were run by standards TAPPI methods. With respect tothe symbols used in the tables: K Number refers to a test for residuallignin shown by oxidation with potassium permanganate, I.V. meansintrinsic viscosity, S10 is the amount of the pulp soluble in 10% NaOHsolution at 20 C., and S18 is the amount of pulp soluble when using 18%NaOH solution at 20 C., S10- Sw corresponds to the true beta cellulosecontent, and R10 is the true alpha. Cuene refers to a standardcupriethylene diamine solution for dissolving cellulose commonly used inthe pulping art which is 100010005 M in copper with an Ene/Cu ratio of20G-2.03 to 1. Cuene IV.s are intrinsic viscosities calculated from thespecific Viscosity of a 0.5% solution of the chlorited cellulosic samplein a 1 to 1 mixure of said cuene and distilled Water.

3 The following examples illustrate operations carried out according tothe process of the invention:

4 EXAMPLE V Hemlock chips (150 g. O.D.) were cooked at 9% EXAMPLE 1Bamboo Gum .Active alkali, percent l 15 12 15 12 15 9 Liquor to woodratio, w./W 5:1 5:1 5:1 5:1 5:1 5:1 5:1 5:1 5:1 Percent su1f0lane 50 5050 50 50 50 50 50 60 Time to, hours.. 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.51.5 Time amhours-. 2 2 2 1.5 1.5 1.5 1.5 1.5 1.5 Temperature, C 170 170170 170 170 170 100 160 100 Yie1d,percent 42.4 44.2 47.2 10.4 42.5 50.252.8 53.5 51.9 Tuning N11 N11 N11 N11 Nil N11 0.175 0.505 1.99 K" 8.29.0 11.0 9.3 10.6 13.4 13.0 14.8 24.8 LV 12.43 13.80 14.13 11.85 13.314.0 11.85 13.60 13.80 S10.. 8.77 9.05 8.01 10.17 13.19 1.134 11.5010.98 8.05 R16-. 91.23 90.35 91.39 89.83 86.81 88.66 88.50 89.02 91.95S18.. 6.85 7.54 0.57 8.10 10.13 9.03 9.08 9.12 7.09 S10-sn 1.92 2.112.04 2.07 3.00 2.31 2.42 1.00 0.96 Xy1an,percent 12.2 13.5 14.3 14.313.9 13.4 13.4 15.5 13.0 Mannan, percent 0.1 0.1 0.1 0. 8 0.9 0.5 0.5 0.7 0. 7 Araban, percent 0. 8 0. 9 1. 0 0 0 0 0 0 0 Galactan, percent 0 00 0 0 Lignin, solubilized, percent 1. 2 0. 54 0.78 0. 05 0. 72 0. 57Lignin, insolubilized, percent 1. 1 1. 5 2. 1 1. 8 2. 6 5. 3 Ash, perf-m2. 58 1. 30

1 Derived entirely from NazS.

EXAMPLE n A.A.-derived entirely from Na2S in sulfolane-Water mixture(50% sulfolane, 5:1 liquor to Wood ratio) at 170 Csdrrgltlg' fgarrod 25C. (1.5 hrs. to TmaX 2 hrs. at Tmax) in stainless steel bombs. Liquorwas then ltered from the chips and they Acme alkali'pement 15 12 9 15 129 were debered (Waring Blendor) in 1% NaOH (21.), iquortto ivldratimw-/w-u 5% 5% 5&1) g washed thoroughly with water and collected in acentri- IC Il S11 O alle Tmgmhoms 1 5 1 5 1 5 1 5 1 5 1 5 30 fuge. Thepulp amounted to a 54.6% yield and had a gime anthours. 173 17g 17g 7g17g 17g Cuene LV. of 18.3.

empera ure, Y1e1d,p5reent 43.4 45.4 48.3 37.0 37.0 39. 0 The resultsfollow 1U Table V Tailings, percent Nil Nil 0. 47 Nil Nil Nil K" Number21.7 20.2 33.8 18.2 20.6 25.4 TABLE V IV 1g' s? lg 1g' g l 11539 1g' 21gActive alkali percent1 9 7 u 92.72? Q 954. 35 Liquor to wood rat1o,w./w.5 :1 X g3 061g -0635 054g o os flffnt Slfolane 150 y an, percen lme t0rs Mannen, percent.. 4.1 4. 2 3.8 3.3 3.3 3.0 T- t h rsbatn percent't" 09 (2g) (2()J Tlme ao Crsl 1 0 a 3C all, perce m Lignin,s01.,pereent 0.380.19 0.20 0.21 0.20 0 40 .:l 576 Lign1n,inso1.,pereenc 3.6 5.1 8.1 3.33.8 5.7 Eril? 1 Pefn' II- l ailings 1 1 S. entlrely from N32 Ku NumberCuene I.V. 18.3 EXAMPLE III S 3 77 Douglasr R10 96.23 .Active alkali,percent l 15 12 9 218%- 10 1a Liquor to wood ratio w./w 5:1 5:1 5:1Percent snlfoia 50 50 50 Xylan Percent -7 4'1 $511615, genre-- 1.5 1.31.3 Mannan, percent 8.2

mie a ours.- Temperature,o 170 170 170 50 fraban flcent 10 $5111,percent-. silig 05155 05% (lalactan, percent 1.2

2.1 lugs, perCBD. K" Number-. 24.1 28.3 32.4 Lfgnfb SOL 0'19 v 46; 174gLignm, insol. 9.4

93193 94163 95160 1 Derived entirely from N528.

4.61 4.21 3.51 11142 125g 018g EXAMPLE VI lflpfrctgg' A Southern pinewood chip furnish in a solution to Galatan,percnt 0.8 0.8 1.1 wood ratioof 5 :1 (50% ethylene glycol), A A. 9, 12, Eggs' ggzeggnh 0-3 ol 0511and 15% provided entirely by NazS was digested for 3, 31/2 hours at 170and 180 C. The results are shown in l Derived entirely from NazS. TableVI EXAMPLE IV Beech White spruce Red spruce Active alkali, percent l 1612 9 15 12 9 15 12 9 Liquor towoodratio,w./w 5:1 5:1 5:1 5:1 5:1 5:1 5:15:1 5:1 Percent suifolene 50 50 50 50 50 50 50 50 50 Time to, hours 1.51.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Timeat,hours 2.5 2.5 2.5 2.5 2.6 2.5 2.52.5 2.5 Temperature, 0.--. 170 170 170 170 170 170 170 170 170 Yield,percent 45.8 53.8 54.5 46.7 49.1 515 53.1 52.7 60.2 Tailings, pereentNil Nil Nil Nil Nil Nil Nil Nil Nil K" Number 9.8 7.0 14.5 13.3 10.1 22619.3 20.2 34.3 LV 13.7 16.2 16.8 13.94 15.9 16.3 15.7

l Derived entirely from NazS.

TABLE VI Active alkali, percent 12 9 15 12 9 Nazsgramsl 46.05 36.8227.62 46.05 36. 82 27.62 Time to, hours. 1. 5 1. 5 1. 5 l. 5 1. 5 l. 5Time at, hours 2 2 2 2. 5 2. 5 2. 5 Temperature, C 170 170 170 180 180180 Yieid, percent. 44. 5 38. 1 38. 3 47. 5 46. 0 38. 9 Tailings,percent. 6. 6 16.4 21.1 4 37 l0"2 1. 55 15.0 iC' Number.. 35. 8 36. 436. 3 27. 1 34.9 37. 2 i5. 07 15.50 15. 50 14. 88 15. 06 14. 86 6. 68 6.05 5. i5 8.09 6. 99 6. 95 93. 32 93. 95 94. 85 91. 91 93.01 93. 05 5. 164. 83 4. 05 6. 43 5. 45 5.26 i. 52 1. 22 1. 10 1. 66 1. 54 1. 69 Xylan,percent 5. 5 6. l 5. 6 5. 5 6. 2 5.3 Mannan, percent... 4. 4 4. 8 4.8 4.3 4. 5 4. 6 Araban, percent... 0. 8 1. 1 1. 0 1. 0 0. 8 1. 0 Galactan,percent 0. 5 0. 5 0. 6 0.4 0. 9 0. 6 Ligniri, solubilized, percent..0.32 0. 16 0.2 0. 26 0. 73 0.42 Lignin, insolubilized, percent 8.9 11. 614. 3 5.0 7.0 12.0

1 6l. 5% NaQS, with remainder Water of crystallization.

oo EXAMPLE VH The W d coold at 1 and 15 hours failed to produce 2() pulpand was discarded. The two hour cook was defbered Western hemlock wasdigested 1n a Solutlon wlth a but was not deiignied to the point whereit was soluble wood ratio of 5: 1, A.A. 15% for 3 hours at 170 C. incuene. Therefore, no I.V. was available. Compared to From theaccompanying graph (FIG. 1) 1t would apother data it would appear thatfor the above conditions pear that at higher concentrations sulfolane isquite elfecthe minimum time needed to produce pulp is on the Order tivefor lignin removal-being less effective at lower con- 0f 2,5 hours.centrations. However, at higher sulfolane concentration, EXAMPLE 1Xcuene I.V.s tend to be lower so that a balance between these two valuesis important. A solution of about Western hemlock wood chips in asolution to wood sulfolane Seems to be near optimum but this ratio couldratio of 5:1 (50% sulfolane by weight), A.A. 9, 12, and vary slightly toeither side of this optimum. The lower 30 15% provided by NagS. As seenfrom the accompanying cuene I.V.s brought about by higher sulfolaneconcengraph (FIG. 2) increase in temperature leads to lower tration doesnot show large variationonly 2.5 units LV. It should be noted, however,that experimental points over the whole range. The results are shown inTable VII. on the graph are extremely limited and the plots are in-TABLE VII Active alkali, percent 1 15 15 l5 15 15 15 Time to,hours..- 1. 5 l. 5 1. 5 1. 5 1. 5 1. 5 Time at, hours. 1. 5 1. 5 1. 5 1.5 1. 5 1. 5 Temperature, 170 170 170 170 170 17() 48. 6 48. 0 50. i 51.1 51. 1 52. 9 23. 7 25. 0 25.4 27. 8 30. 6 31.1 11.2 12. 0 12.7 13. 813. 3 13. 7 7. 29 7. 13 6. 30 6. 92 6. 33 5. 14 92. 71 92.81 93. 70 93.08 93. 67 94. 86 5. 54 5. 28 4. 51 4. 19 4. 43 3. 77 1. 75 1. 85 1. 792. 73 1. 90 1.37 6.4 5.6 6.6 6.1 5.9 5.5 6.8 6.3 6.7 6.0 5.6 5.4 0.9 0.90.0 0.8 0.8 0.8 Galactan, percent 0. 7 0. 6 0. 6 0. 7 0. 6 0. 7 Lignin,solubilized, percent 3. 5 3.6 4. 1 5. 0 6. 5 7. 5 Lignin, insolubilized,percent 0.36 0.48 0. 36 0. 2.1 0. 1 2 0. 0 8 Tailings, percent Nil NilNil N11 N11 N11 Percent sulfolane in liquor (w./w.) 63 57 43 36 30 1Derived entirely from NagS.

EXAMPLE VIII In this example a western hemlock wood furnish in tended toindicate trends only. Yields, K number, and lignin values vary inverselywith temperature. Generally,

a solution to wood ratio of 5 :1 (50% sulfolane by 55 the relationshipsare those to be expected from temperaweight), with an A.A. of 10%, wasdigested for 1, 1.5 and 2 hours at 170 C. The only alkali added wasNazS.

ture increase. The results of these tests are also shown in Table IX.

TABLE IX Active alkali, percent l5 12 9 15 l2 9 12 15 9 NagS, grams l46.05 36. 82 27.62 46. 05 36. 82 27. 62 36. 82 46.05 27. 62 Time to,hours.. 1. 5 1. 5 1. 5 1. 5 1. 5 1. 5 1. 5 1. 5 1. 5 Time at, hours.. 1.5 1. 5 1. 5 1. 5 l. 5 1. 5 l. 5 1. 5 l. 5 Temperatuie, 180 180 180 190190 190 170 170 170 Yield, percent. 43. 5 49.1 51.3 38. 4 46.1 49. 4 53.4 48. 9 55.8 Tailings, percent. Nil Nil Nil Nil Nil Nil Nil Nil O. KNulnber. 16. 4 20. 7 29. 4 10. 5 13. 7 21. 2 33. 5 28. 9 37. 0 LV 14.0015. 5 16.2 12. 6 14. 5 15. 75 17. 30 16. 35 16.88 Sm.. 6. 91 6.04 4. 608. 28 7. 20 5. 84 4. 2() 5. 16 3. 55 R10. 93.09 93. 96 95.40 91. 72 92.8O 94. 16 95. 80 94. 94 96. 45 Sigh.. 6. 01 5. 20 4. 10 7. 35 6.47 5. 183. 82 4. 35 3. 04 SMASH; 0. 0. 84 0. 50 0. 93 0. 73 0. 66 0.38 0. 7l 0,51 Xylan, percent. 3. 7 4.0 3. 6 3. 7 4. 2 5. 1 3. 2 2. 7 2. 5 Manuali,percent. 6. 4 6.2 6.0 6. 0 6. 3 8.2 6. 9 5. 7 4. 9 Araban, percent. 0. 50. 7 0. 7 0. 6 0. 7 0. 8 0. 7 0. 5 0. 7 Galactan, percent O. 6 0. 8 0. 90. 7 0. 6 0. 7 l. 0 0. 5 O. 5 Lignin, solubilized, percent. 0. 27 0. 270. 27 0. 38 0. 31 0. 32 0.26 0. 27 0. 34

Ligniii, insolubilized,

percent 2. 7 4. 0 6. 5 1. 5 2. 6 4. 1 7. 4 6. 0 10. 8

l 61.5% NazS with remainder water of crystallization.

EXAMPLE X.-WOOD FURNISH-WESTERN HEMLOCK CHIPS Active alkali, percent 1515 15 15 15 15 Liquor to wood ratio, w./W 5:1 5:1 5:1 5:1 5:1 5:1Sulfidity, percent 100 100 100 100 100 100 Time to, hours 1. 5 1. 5 1.5 1. 5 1. 5 1. 5 Time at, hours 1. 5 1. 5 1. 5 1. 5 1. 5 Y 1. 5Temperature, C 170 170 170 170 170 170 Yield, percent 48. 6 48.0 50. 161.1 51. l 52.9 K Number- 23. 7 25.0 25.4 27. 8 30. 6 31. 1 11. 2 12. 012. 7 13. 8 13. 3 13. 7 7. 29 7. 13 6. 30 6. 92 6. 33 5. 14 92. 71 92.81 93. 70 93.08 93. 67 94. 86 5. 54 5. 28 4. 51 4. 19 4. 43 3. 77 1.75 1. 85 1. 79 2. 73 1. 90 1. 37 6.4 5.6 6.6 6.1 5.9 5.5 6.8 6.3 6.7 6.05.6 5.4 Araban, percent 0. 9 0. 9 0. 9 0. 8 0. 8 0. 8 Galactan, percent0.7 0. 6 0.6 0.7 0. 6 0.7 Lignin, solubilized, percent- 3. 5 3. 6 4. 15. 0 6. 5 7. 5 Lignin, insolubilized, percent 0.36 0.48 0.36 0.21 0. 120.08 Tailings, percent Nil Nil Nil Nil Nil Nil Percent sulfolane inliquor (w. 70 63 57 43 36 30 NOTE: The eiect of the variationillustrated in FIG. 1.

We claim:

1. In the pulping 0f wood chips in aqueous alkaline solutions in whichthe entire active alkali is essentially sodium sulde, the improvementwhich comprises digesting the wood chips in such aqueous alkalinesolution in combination with an organic solvent for lignin at atemperature of Ifrom about 160 C.-190 C. for a period of from about 25-4 hours to produce a pulp having cuene I.V. values varying from to 18and being soluble in cuene after chloriting, said solvent being selectedfrom the group consisting of alkyl polyols, cyclic sulfones, acylicsulfones, and mixtures thereof and the amount of solvent in thecombination varying from about 30 to 70 percent.

2. In the process of claim 1 the aqueous solution containing from 9 to15% active alkali added as sodium sulde and the organic solvent is asulfone.

3. The pulping process of claim 2 in which the digestion solution towood chip ratio is 5:1, the sulfone t0 water ratio is 1:1 by weight, thedigestion temperature is about 170 C. and the digestion time is about3.5 hours.

in sulfolane to water ratio (w./w.) is graphically References CitedUNITED STATES PATENTS 12/1935 Dreyfus l62-76 X 3/ 1940 Peterson 162-72 XHOWARD R. CAINE, Primary Examiner U.S. C1. X.R. 162-77 O i, UNITEDSTA'IES PATENT OFICE CERTIFICATE GF CORRECTION Patent No. 3,513,069Dated May 191, 1970 Inventor(s) LAURENCE D. STARR and RONALD L. CASEBIER1 It is certified that error appearsQ-in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column l, line 18, "eyceptionally" should be -exceptionally Column l,line 50, V"lign" should be lignin Column 2, line 18, "hemicullulose"should be --heaemicelltllosel Column 2, line 42, .derivedf" should lbedesired Column 2, line 49, "standards" should standard Column 3.4,Example I, Table, 6th numbered column, 10th number dow:

"1.134" should beA jl1.34

SIGNED AND SEALED ml E. Wm, JR. Ofr Gamissioner of Patents

